1. Field of the Invention
The present invention relates to an optical scanning device, and more particularly to an optical scanning device provided with a plurality of light sources.
2. Description of the Related Art
An image forming device using electrophotography (such as a multi function peripheral (MFP) provided with the scanner function, facsimile function, copying function, function as a printer, data communication function, and server function, a facsimile machine, a copier, a printer, and the like) may be configured to form an image by scanning the surface of an image carrier with a light beam emitted from an optical scanning device which is supported by a support member in the image forming device.
In particular, an image forming device configured as a tandem full-color printer includes therein an optical scanning device which outputs four laser beams including image information of yellow (Y), magenta (M), cyan (C), and black (K), respectively. The four laser beams enter into photoreceptor drums of the corresponding colors, whereby a tandem laser scanning optical device is established.
The optical scanning device includes therein a polygonal rotating mirror (i.e. a rotating reflector or a polygon mirror), a scanning lens (i.e. a fθ lens), a retroreflector, a reflector, a cylindrical lens, and other components. The optical scanning device further includes therein four laser light sources (which may also be simply referred to as “light sources”) which output four laser beams. This enables image exposure processing for the four photoreceptor drums (i.e. image carriers).
In the conventional laser scanning optical devices, it is known to integrate the substrates for a plurality of laser light sources into one piece.
Specifically, Documents 1 and 2 below each disclose a configuration in which a plurality of substrates are integrated into one piece by arranging the laser light sources slantwise. In each configuration, securing units provided on the device housing side and for holding the substrate are arranged in a longitudinal direction. Substrate holding portions formed in the substrate each have a circular hole shape, and the substrate is fixedly secured to the housing by screws.
Document 3 below discloses a configuration in which a plurality of substrates are arranged on an attachment base member so as to integrate the substrates into one piece.    [Document 1] Japanese Patent Application Laid-Open No. 2007-79400    [Document 2] Japanese Patent Application Laid-Open No. 2008-97920    [Document 3] Japanese Patent Application Laid-Open No. 2006-227494
In recent years, color copiers, printers, and other image forming devices have been increasingly reduced both in size and cost. In particular, there is a demand for reduction in height of the devices. In terms of the optical devices, there is a demand for reduction in size in the sub-scanning direction.
In the case where it is tried to reduce the size (particularly the size in the sub-scanning direction) of the light source unit (including the light source, light-source holding member, substrate, and substrate holding portion) in the conventional configuration, however, the distance between the securing units arranged on the housing side and for holding the light-source holding member cannot be decreased without impairing the precision in holding the light source.
Furthermore, when the substrate holding portion is in a circular hole shape, a large area is required for securing the shape on the substrate, leading to an increase in size of the substrate and, hence, of the device. Still further, connectors connected to the substrate need to be arranged carefully in order to reduce the size of the device.